How to build an offline supporting web application with AngularDart

We have been starting out on building a simple web application on AngularDart 2.

What is the best way to have it runnable on the clients even though they lost internet connection? Right now I am using Lawndart library to use the local storage for saving some data received from REST-Api and it's working fine. But I haven't figured out how to tell the client browsers to cache all sources and use them when having no internet connection. (Right now I am simply using my Redstone-Dart Server (on which the REST-Services are running) for providing the sources)

It is easy to setup (just serve a manifest.appcache). For angular application, it mostly contains index.html, main.dart.js and external dependencies.
For me it works on Safari, Chrome and Firefox (cannot tell for IE/Edge). As iOS was a need for me, I could not find another alternative (service worker). Chrome is starting to send a warning for non https sites but so far so good.

Real push notifications are more complex in a web environment; I personally use Firebase realtime database to "push" updates

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